Allen Kelsey Grammer (born February 21, 1955) is an American actor, comedian, and producer. He gained fame as the psychiatrist Dr. Frasier Crane on the NBC sitcom Cheers (1984–1993) and its spin-off Frasier (1993–2004, and again from 2023 to 2024). At over 20 years on-air, this is one of the longest-running roles played by a single live-action actor in primetime television history. He has received numerous accolades, including six Emmy Awards, three Golden Globe Awards, a Screen Actors Guild Award and a Tony Award.

Having trained as an actor at Juilliard and the Old Globe Theatre, Grammer debuted as Lennox in the 1981 Broadway revival of Macbeth. The following year, he portrayed Cassio as the opposite of Christopher Plummer and James Earl Jones in Othello. In mid-1983, he acted alongside Mandy Patinkin in the original off-Broadway production of Stephen Sondheim's musical Sunday in the Park with George. He has since starred in the leading roles in productions of both Sweeney Todd: The Demon Barber of Fleet Street and My Fair Lady.

On film, he is known for his role as Dr. Hank McCoy / Beast in the superhero films X-Men: The Last Stand (2006), X-Men: Days of Future Past (2014) and The Marvels (2023). His other roles include Down Periscope (1996), The Pentagon Wars (1998), and Swing Vote (2008). He is also known for his voice roles in Anastasia (1997), Toy Story 2 (1999), and as Sideshow Bob in The Simpsons (1990–present). He took guest roles in the sitcoms 30 Rock (2010–2012), Unbreakable Kimmy Schmidt (2016), and Modern Family (2017). For his performance as the corrupt mayor in the Starz political series Boss (2011–2012), he received a Golden Globe Award for Best Actor – Television Series Drama.

In early 2010, Grammer returned to Broadway in the musical revival of La Cage aux Folles, where he received a nomination for the Tony Award for Best Leading Actor in a Musical. In mid-2016, Grammer won a Tony Award for Best Musical as producer of a musical revival of The Color Purple. In early 2019, he starred as Don Quixote in a production of Man of La Mancha at the London Coliseum. In late 2023, The Telegraph described Grammer as one of "the finest actors" of his generation. He was awarded a star on the Hollywood Walk of Fame in mid-2001.